MARIN — Starfish here are dying at an alarming rate, and researchers at the Romberg Tiburon Center for Environmental Studies are trying to understand why.

The phenomenon is not limited to Marin; up and down the West Coast a variety of species of the beloved starfish are literally wasting away. The malady has been dubbed Sea Star Wasting Disease.

First seen off British Columbia in 2013, the disease has been logged in waters from Alaska to Mexico, but has also appeared on the East Coast and as far away as China.

The initial indicator is the twisting and contorting of the sea star’s arms, followed by white lesions on the body. Finally the arms fall off and the starfish dies. More than 20 sea star species have been affected.

“It’s a gruesome process,” said Drew Harvell, of Cornell University, who spoke on the issue last week at San Francisco State University’s Romberg Center. “This is the largest marine life (disease) we have experienced in the oceans.”

Romberg researchers are on the case, having surveyed five sites in Marin since June: Point Bonita, Rodeo Beach, Muir Beach, Slide Ranch and Duxbury Reef.

“They all show very steep declines in sea star abundance,” said researcher Sarah Cohen, a biology professor. “We are specifically focused on the sea stars that initially showed some apparent resistance to the disease.”

But in three of the locations, Cohen and her team were unable to find any of those species. In the other two locations, their abundance had dropped significantly.

“It is really unfortunate that the apparently resistant species are also showing strong signs of wasting disease impacts,” Cohen said. “This group of small stars is actually several species. Some of them have gone extinct locally, apparently in multiple locations.”

Tiburon researchers will continue to look at the issue is hopes of better understanding the die-off and why it is occurring and how different species are affected.

Harvell and her colleagues at Cornell have preliminary linked the disease to what is know as densovirus, essentially a viral infection.

“It has always been there, but it has become an opportunistic pathogen, maybe because of climate change, stressful conditions and changed pH in the water,” said Laura Melroy, a Romberg researcher studying the issue. “The virus has been around, but is now affecting sea stars as they are stressed.”

Given a changing climate, Harvell said changes in the ocean were expected, but nothing this dramatic.

“This is an event that all took us by surprise,” she said, speaking to about 100 people at the Romberg event. “We don’t know what changed. Some of it lies in the genetics of that virus.

“We are under very unusual warm conditions in our oceans on our Pacific Coast,” said Harvell, noting a recent 9-degree temperature change. “But there is no evidence warm waters triggered the outbreak, but it did make mortality more rapid.”

The sea star issue has gained attention because of the invertebrates are so well known. Often brightly colored, the sea stars can live up to 35 years in the wild. Their vital organs are located in their arms, but they do not have a brain. Their small, suction-cupped feet in the shape of tubes pry open clams or oysters for nourishment.